高性能交流感應主軸馬達驅動器之平行處理即時適應控制之研究

Abstract

本論文發展高性能電腦數值控制工具機交流感應主軸馬達之即時適應 控制技術，同時發展以傳輸電腦為基礎的平行處理技術來實現複雜且需即 時處理的適應控制法則，使其速度響應具有適應於負載變動、參數變化、 與負載轉矩干擾之能力。此控制系統包含速度適應控制、轉矩適應控制、 與電流適應控制，在轉矩適應控制中包含磁場導向向量控制、負載轉矩估 計與前授補償、與弱磁控制。速度適應控制器位於磁場導向向量控制迴路 之前，含有一個二自由度速度控制器、一個伺服受控模型參數估測器、與 一個速度控制器參數調變機制。速度控制器之設計採用極點植根法，此法 利用多項式處理方式調整控制器參數。伺服受控模型參數估測器採用二階 遞迴恆跡最小平方法，以避免在長時間內無激盪信號而產生估測終結現象 。電流適應控制器工作在二軸靜止座標系以便提供持續激盪條件，在二軸 中各含一個參數估測器、一個預測型電流控制器、與一個電流控制器參數 調變機制。其中參數估測採用一階四維遞迴可變遺忘因子最小平方法，以 估測出馬達參數變化與反抗電動勢。轉矩適應控制器位於電流控制迴路之 前，其前授負載轉矩補償器的設計乃基於一個受估測的負載轉矩模型。此 負載轉矩的估測使用一階三維遞迴可變遺忘因子與共變率重置最小平方法 ，以偵測出緩慢或快速的負載轉矩變化。此外，本文亦提出一個PWM脈波 產生方法，此方法利用空間向量的概念，具計算簡單之特性。整個適應控 制系統的計算執行非常複雜，但因其為多巢迴路，隱含平行計算之特性， 故將其平行化且安裝於IMS T800傳輸電腦上。 為了實現此平行適應控 制法則，本論文提出一個即時控制的整合性平行控制器架構，並分別研製 出以傳輸電腦為基礎之平行計算與I/O 模組電路板，藉由這些模組的擴充 ，此平行控制器能增加其計算與I/O處理能力。亦在一個PC電腦上發展交 談性軟體以便和此控制系統連接。平行控制軟體乃以高階語言Occam來實 現。此平行控制器在性能與架構上與其他兩個平行控制器相比較，顯現其 優異性。實驗結果驗證此一適應控制系統可使感應馬達在負載變化時仍能 保持良好的轉矩電流與轉速動態響應，此結果可為未來發展高轉速與高功 率的數值控制工具機交流感應主軸驅動器奠立良好之基礎。 In this dissertation, we develop a real-time adaptive control technique, which enables the high-performance control of an ac induction spindle motor drive for CNC machine tools, and develop a transputer-based parallel processing technique for the realization of the complicated and real-time adaptive control algorithm. The induction spindle drive can adaptively regulate the speed performance in contending with varying load, torque disturbance, and motor parameter variations. The control system consists of adaptive speed control, adaptive torque control, and adaptive current control. The adaptive torque control comprises rotor-time constant adaptation for field-oriented vector control, load-torque estimation and feedforward compensation, and field-weakening flux control. The adaptive speed controller, which precedes the field-oriented control loop, consists of a two-degree-of-freedom controller and a speed-controlled plant model estimator. The two-degree-of-freedom controller is designed by a pole-placement technique with polynomial manipulations. Its parameters are adjusted adaptively in terms of estimated model parameters. Estimating the model parameters entails a second-order least-squares estimator with constant trace to avoid estimator windup. The adaptive current controller, operating in the stationary two-axis frame for providing the persistently exciting condition for parameter estimation convergence, consists of an one-step-ahead predictive controller and a model estimator. The predictive controller*s parameters are adjusted adaptively in terms of estimated model parameters. Estimating the model parameters entails a first- order four-dimensional least-squares estimator with variable forgetting factor to detect the variations of the motor parameters and back emf. In the adaptive torque controller, which precedes the current control loop, the design of the feedforward load torque compensator is based on an estimated load-torque model. Estimating the load torque entails a first- order three-dimensional least-squares estimator with variable forgetting factor and covariance resetting, whose purposes are to detect any slow or sudden changes of torque disturbance, respectively. A simple implementation scheme for the PWM waveform generation, which modulates the current control outputs as three-phase PWM pulses to drive the motor, based on space vector concept is also presented. The computation of the resulting adaptive speed, torque, and current controller is very complex. However, the system exhibits some implicit parallel characteristics because of the nested control loops. So, it has been implemented in parallel by IMS T800-20 transputers. For the realization of the parallel adaptive control algorithm, a unified controller architecture comprising transputer-based parallel computing boards and input/output boards suitable for the real-time control of various types of motor drives is also presented. The system can increase its computing and input/ output processing capability by paralleling these boards. A host server based on a personal computer for user interface is also developed. The control functions can easily be implemented in parallel by using the high-level programming language Occam. A comparison with two existing parallel controllers shows the performance and architecture features of the system. Experimental results show that the adaptive control system maintains the desired torque-producing current and speed performance in the presence of varying load and disturbance. The work can be the basis of the research for high-speed and high- power ac induction spindle drive for CNC machine tools in the future.